In the field of vehicle repair, on those vehicles equipped with an electronic control module it is often required to do voltage and continuity testing of wires electrically connected to the electronic control module and to various computer controlled electronic devices on the vehicle. This has often presented problems in the past, not the least of which is the access for testing of the pins of the module itself, which is often located underneath the dashboard. Also, there are often problems at the end of the electrical harness which connects to the module. The harness usually carries about 52 wires, each of which connects one of the controlled devices on the vehicle to the electronic control module through the various wires of the harness. These two, the connector at the harness end and the module pins are often at relatively inaccessible locations; or, if accessible, the same can only be tested by a person in an inconvenient contorted position. In addition, such testing which is conventional has been extremely time-consuming and not always accurate because of the foregoing.